Concentrated aqueous nanocomposite dispersions for barrier coatings

ABSTRACT

A concentrated nanocomposite dispersion which includes a silicate filler and a matrix polymer dispersed in an aqueous medium. The dispersions are condensed by selectively removing liquid therefrom, to provide high solids coating formulations. The concentrated formulations provide coatings which are good barriers to oxygen and other gases.

CLAIM FOR PRIORITY

This non-provisional application is based upon U.S. Provisional patentapplication Ser. No. 60/846,226, of the same title, filed Sep. 21, 2006.The priority of U.S. Provisional patent application Ser. No. 60/846,226is hereby claimed and the disclosure thereof is incorporated into thisapplication by reference.

FIELD OF INVENTION

The present invention relates generally to nanocomposite dispersionswhich are used to provide coatings having enhanced barrier properties.Specifically, the invention relates to nanocomposite dispersions whichinclude exfoliated silicate filler, a film forming polymer, and water.The dispersions are condensed by selectively removing a portion of theaqueous medium.

BACKGROUND OF THE INVENTION

Barrier coatings which prevent, reduce, or inhibit the permeation of aselected substrate with a gas, vapor, chemical and/or aroma have beenwidely described, and such coatings are used in a variety of industries,e.g., the packaging industry, automobile industry, paint industry, andtire industry. For example, butyl rubber in automobile tires has beencoated with formulations which includes a polymer and a platelet filler,in order to reduce the air permeability of the tire. See, e.g., U.S.Pat. Nos. 4,911,218 and 5,049,609. Tires with integral innerliners aredisclosed in U.S. Pat. No. 5,178,702, wherein the tire includes rubberlaminate in which at least two layers are barrier layers having 100parts by weight rubber, 100 parts by weight acrylonitrile/diene polymerand about 25-150 parts by weight of platelet filler of unspecified widthand thickness. These compositions are stated to reduce the costs of theinnerliners while maintaining flexibility and barrier performance.

The use of exfoliated silicates to produce nanocomposite barriercoatings has been achieved by several methods. The most widely used hasbeen by combining a dissolved polymer with exfoliated filler. Watersoluble polymers such as polyvinyl alcohol (PVOH) have been combinedwith water exfoliated filler such as vermiculite. See, Japan Patent11-246729, Sep. 14, 1999, “Gas-Barrier Poly(vinyl alcohol)/poly (acrylicacid) Compositions and their Laminates and Shaped Articles.” SumitomoChemical Co., Ltd. Polycarbonate polymers have been dissolved in tolueneand combined with organically functionalized filler to form good barriercoatings. W. J. Ward et al., “Gas Barrier Improvement Using Vermiculiteand Mica in Polymer Films”, Journal of Membrane Science, 55:173-180(1991)]. Other polymers have also been made into improved barriercoatings by dissolving them in a solvent, and using an organicallyfunctionalized filler to improve the barrier properties. See, e.g.,Yano, K. et al., “Synthesis and Properties of Polyimide-Filler HybridComposites”, Journal of Polymer Science A: Polymer Chemistry, 35, 2289(1997).

There are several examples of using an aqueous dispersion of exfoliatedfiller with an aqueous dispersion of polymer to form a nanocomposite.Most of that work used elastomeric polymers in suspension. See, forexample, Wu, Y-P et al., “Structure of CarboxylatedAcrylonitrile-Butadiene Rubber (CNBR)-Filler Nanocomposites byCo-coagulating Rubber Latex and Filler Aqueous Suspension”, Journal ofApplied Polymer Science, 82, 2842-2848 (2001); Wu, Y-P et al.,“Structure and Properties of Nitrile Rubber (NBR)-Filler Nanocompositesby Co-coagulating NBR Latex and Filler Aqueous Suspension”, Journal ofApplied Polymer Science, 89, 3855-3858 (2003); Varghese andKarger-Kocsis, “Natural Rubber-Based Nanocomposites by Latex Compoundingwith Layered Silicates”, Polymer (in press) (2003); Feeney et al., U.S.Pat. No. 6,087,016, “Barrier Coating of an Elastomer and a DispersedLayered Filler in a Liquid Carrier”, Jul. 11, 2000; Feeney et al., U.S.Pat. No. 6,232,389, “Barrier Coating of an Elastomer and a DispersedLayered Filler in a Liquid Carrier and Coated Articles”, May 15, 2001;Goldberg et al., “Nanocomposite Barrier Coatings for ElastomericApplications”, Materials Research Society, Symposium T: Polymernanocomposites, paper T4.7, (April 2002); and Goldberg et al,“Elastomeric Barrier Coatings for Sporting Goods”, ACS Rubber Section,Apr. 29, 2002, paper 17, published in Rubber World, vol. 226, No. 5, p.15 (August 2002).

Other references of interest include U.S. Pat. No. 4,472,538 toKamigaito et al.; U.S. Pat. No. 4,889,885 to Usuki et al.; U.S. Pat. No.6,087,016 to Feeney et al.; and U.S. Pat. No. 6,232,289 to Feeney et al.

Despite the contributions in the art, there exists a need for an aqueouscoating composition that exhibits enhanced barrier properties, which maybe applied to other polymer films. Such a coating would be particularlyuseful in packaging applications where the package contents spoil ordegrade upon contact with air. There further exists a need for a coatingmaterial which can be provided in a processable and economical form,whereby the coating can be produced at a high solids content withoutgelling.

SUMMARY OF THE INVENTION

According to one aspect of the present invention there is provided aconcentrated dispersion for forming a nanocomposite barrier coating on asubstrate, where the barrier coating includes (a) a liquid carriermedium which is primarily water, i.e., at least 50 wt. %; (b) anexfoliated silica filler material that is dispersed in the liquidcarrier medium; and (c) a matrix polymer which is dispersed in thecarrier medium. The dispersions are concentrated by dispersing thefiller material and polymer matrix in the liquid medium, and increasingthe solids content of the initial dispersion by selectively removing aportion of the liquid carrier medium prior to applying the dispersion tothe substrate. The method of preparation of the concentrated dispersionsimparts unique characteristics and is intended as a feature of thedispersion and coatings, not merely a step in the preparation thereof.

Still further features and advantages of the invention are apparent fromthe following description.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in detail below with reference to thedrawing:

FIG. 1 is a diagram showing the oxygen permeability values of threecompositions prepared according to different methods, where it is seenthat the concentrated dispersions of the invention have the lowestpermeability.

DETAILED DESCRIPTION OF THE INVENTION

The invention is described in detail below for purposes of illustrationonly. Modifications within the spirit and scope of the invention, setforth in the appended claims, will be readily apparent to one of skillin the art. Unless defined otherwise, terminology and abbreviations, asused herein, have their ordinary meaning.

The phrase “concentrated dispersion,” “concentrated nanocompositedispersion,” or like terminology refers to a suspension, dispersion,emulsion, or slurry of exfoliated silicate filler material and a matrixpolymer in a liquid carrier medium, where the dispersion is concentratedby removal of a portion of the liquid carrier medium.

The term “nanocomposite” or “filled polymer nanocomposite” refers to themixture of substantially exfoliated filler and polymer.

The “oxygen transmission rate,” or “OTR,” of the coatings used in theinvention is measured according to ASTM D-3985-02 or any other suitableprotocol using a MOCON® OXTRAN 2/20 module and the following conditions:pressure of 1 atm, a temperature of 23° C., and a relative humidity of0%.

The present invention relates to nanocomposite coating formulations thatinclude, at a minimum, exfoliated silicate filler material and a matrixpolymer which are dispersed in a liquid carrier medium. The coatingformulations of the invention are concentrated dispersions which have aunique method of preparation—the silicates and the polymer matrix aredispersed in a liquid carrier medium, and then a portion of the liquidmedium is selectively removed from the dispersion, such that the solidscontent of the dispersion is increased.

The liquid carrier medium used in the invention is aqueous; that is, itis at least 50 percent water, and typically consists essentially ofwater. Minor amounts of organic solvents may be included in the carriermedium if desired. Suitable solvents may include ethanol, methanol,isopropanol, toluene, hexane, other hydrocarbons, and combinationsthereof.

The exfoliated silicate filler materials which are dispersed in theliquid carrier medium include layered clay compounds which are made ofplatelets having a high aspect ratio. “Exfoliation” is defined forlayered fillers as the separation of individual layers of the plateletparticles; the filler material used in the invention is at leastpartially exfoliated, and preferably is substantially exfoliated. Theaspect ratio is the product of the lateral dimension of a plateletfiller particle divided by the thickness of the platelet. The aspectratio of the filler used in the invention is typically at least 50, atleast 1,000, and preferably at least 5,000 up to about 30,000. Thethickness of at least some filler particles is below 1 micron, andprobably well below 100 nm, preferably less than 10 nm. The exfoliatedsilicate filler material may include, for example, bentonite,vermiculite, montmorillonite, nontronite, beidellite, volkonskoite,hectorite, saponite, laponite, sauconite, magadiite, kenyaite, ledikiteand mixtures thereof. The most preferred fillers are montmorrilonite orvermiculite. Suitable montmorillonites are commercially available asSCPX-2973 exfoliated montmorillonite slurry, SCPX-2953 exfoliatedmontmorillonite solid, and SCPX-2041 exfoliated montmorillonite solidand slurry, all from Southern Clay Products (Gonzales, Tex.).

The silicate filler material may be acid or base pre-treated as is knownin the art. The preferred acids for filler pre-treatment are selectedfrom acetic acid, glycine and citric acid, and the preferred bases areselected from ammonium hydroxide, sodium hydroxide and potassiumhydroxide. The amount of acid or base employed should be in the amountof from about 10% to about 20% by weight of the dried barrier coating.

The exfoliated filler material is present at between about 5 to about80% by weight of the total solids of the coating formulations, andpreferably from 20 to 50 weight percent of the total solids. Thecompositions of the present invention, when dried, retain the filler inwell-dispersed form, resulting in greatly improved permeabilityproperties.

The matrix polymers useful in the coating formulations of the presentinvention are not particularly limited. The matrix resins may includehomopolymers and/or copolymers, and are dispersed in the liquid carriermedium as an emulsion or latex. The matrix polymer forms a film in theinventive coatings, in which the platelet particles are dispersed toform a nanocomposite barrier coating. The matrix polymer may be presentin amounts of from 5 to 80 weight percent of the total solids in thedispersion, preferably from 30 to 60 weight percent.

Preferred resins include polymers selected generally from among manyclasses. The selected polymers may be curable polymers, partially curedpolymers, or uncured polymers, and are dispersible in water. Suchpolymers include, without limitation, olefinic thermoplastic elastomers;polyamide thermoplastic elastomer; polybutadiene thermoplasticelastomer, e.g., syndiotactic 1,2-polybutadiene thermoplastic elastomer;polyester thermoplastic elastomer; polyurethane thermoplastic elastomer,e.g., thermoplastic polyester-polyurethane elastomer, and thermoplasticpolyether-polyurethane elastomer; styrenic thermoplastic elastomer;vinyl thermoplastic elastomer, e.g., polyvinyl chloride polyol (pPVC).

A variety of rubbery polymers may also be employed as the polymercomponent of the inventive method, including acrylic rubber, such asethylene-acrylate copolymer; and butadiene rubber, such aspolybutadiene. Still other polymers are chlorosulfonated polyethylenerubber, e.g., chlorosulfonated polyethylene; epichlorohydrin rubber,such as polyepichlorohydrin (CO), polyepichlorohydrin copolymer;ethylene-propylene rubber, such as ethylene-propylene copolymer,ethylene-propylene-diene copolymer. Other suitable polymers may includefluoroelastomers, for example, vinylidene fluoride-hexafluoropropylenecopolymer; natural rubber; neoprene rubber such as polychloroprene;nitrile rubber, for example, acrylonitrile-butadiene copolymer;polysulfide rubber; polyurethane, for example, polyester urethane, andpolyether urethane; propylene oxide rubber; silicone rubber, forexample, methylvinyl-fluorosilicone, and styrene-butadiene rubber, forexample, styrene-butadiene copolymer.

Non-elastomeric polymers may also be used, including polyesters,polyamides, chlorinated polymers, polyolefins, polyurethanes,polyethers, polyketones, polycarbonates, acrylics, vinylics, andflouropolymers. Non-elastomeric polymers are generally considered to bethose which have a glass transition temperature of greater than 23° C.,and/or those with crystallinity above 10%.

Suitable polymers include polyester resins, such as those which arecommercially available as Eastek (Eastman Chemical Company, KingsportTenn.). The Eastek polymers are sulfopolyesters with a Tg of from about30 to 35° C.

The barrier coating formulations of the invention may optionally employat least one or more than one suitable surfactant to reduce surfacetension, and aid in dispersion. Surfactants include materials otherwiseknown as wetting agents, anti-foaming agents, emulsifiers, dispersingagents, leveling agents etc. Surfactants can be anionic, cationic andnonionic, and many surfactants of each type are available commercially.A suitable surfactant for inclusion in these compositions possesses acritical micelle concentration sufficiently low to ensure a driedbarrier coating uncompromised by residual surfactant. In the event of anunfavorable interaction of the anionic emulsifier present in the latexdispersion, additional ionic additives should be kept to a minimum. Thisvariable is eliminated where the surfactant or emulsifier is non-ionic.Increase in ionic concentration of the compositions, such as by theaddition of a base to adjust pH, e.g., KOH, NH₄OH and NaOH, may causeagglomeration of the filler, which adversely affects permeabilityreduction.

Desirable surfactants may include SURFYNOL® PSA 336 (Air Products,Inc.), SILWET® L-77 (OSI Specialties, Inc.), and ZONYL FSP and 8952(DuPont Performance Chemicals and Intermediates). The amount and numberof surfactants added to the coating composition will depend on theparticular surfactant(s) selected, but should be limited to the minimumamount of surfactant that is necessary to achieve wetting of thesubstrate while not compromising the performance of the dried barriercoating. For example, typical surfactant amounts can be less than orequal to about 15% by weight of the dried barrier coating.

The dispersions may also include additional additives such as biocides,colloidal dispersants, anti-foaming agents, dispersing agents, wettingagents, leveling agents, and thickeners. Other optional components ofthe coating mixture include conventional agents to adjust pH, such asbases, e.g., NH₄OH, NaOH or KOH; or acids, e.g., acetic acid, citricacid or glycine provided that care is taken to avoid agglomeration, asdiscussed above.

Further details as to compositions and methods of forming coatings arefound in copending U.S. patent application Ser. Nos. 11/113,349;11/272,351; 10/741,741; 10/741,251; and 10/742,542, the entireties ofwhich are incorporated herein by reference.

As noted above, the dispersions of the invention are produced accordingto a method whereby the silicate filler and polymer component aredispersed in the liquid medium at a given concentration, and thisinitial dispersion is subsequently condensed by selectively removing aportion of the liquid carrier medium. In the condensing step, a portionof the liquid carrier medium is selectively removed to increase thesolids content of the dispersion. Suitable removal methods includeevaporation, distillation, and the like. The liquid may be evaporatedoff by heating; preferably at a temperature of from about 80° C. toabout 100° C. for about 70 to about 100 minutes while stirring untilabout 1% to about 30% of the liquid carrier evaporates.

The dispersions are typically condensed such that the solids content ofthe dispersion increases by at least 5%, i.e., has a solids content ofat least 1.05 times that of the initial, unconcentrated dispersion. Morepreferably, enough liquid is removed such that the solids contentincreases by at least 25% or at least 50%. The concentrated dispersiongenerally includes from about 5 to 25 weight percent solids, andpreferably from about 7 to 15 weight percent solids. Before it isconcentrated, the dispersion typically includes from about 3 to 7 weightpercent solids. It is unexpected that the dispersion may be concentratedby evaporation without causing the formulation to gel. For example, manysilicate filler materials, such as montmorillonite, form gels atrelatively low solids content, and the solids content of the silicatecomponent often limits the final solids content of the barrier coating.

The coating formulations of the invention are generally applied to asubstrate and dried to form a low permeability barrier coating. Thecoating films that are produced provide an excellent gas barrier.Generally, the coatings produced according to the invention exhibit areduction in oxygen permeability of at least 100-fold as compared to asimilar barrier coating which does not include silicate filler material.More preferably, the barrier coating produced according to the presentinvention exhibits at least a 200-fold, at least a 400-fold, and evenmore than 900-fold reduction in gas permeability as compared to abarrier coating which does not include the silicate filler material.Suitable permeability values for the coating may be less than 0.02cc-mm/m²-day-atm, or less than 0.01 cc-mm/m²-day-atm.

Furthermore, it has been surprisingly discovered according to thepresent invention that coatings which were made from concentrateddispersions, i.e. condensed, exhibit superior oxygen barrier propertiesas compared with a like coating (same composition and thickness) whichis prepared from a like dispersion that did not undergo selectiveremoval of the liquid carrier medium, i.e., a dispersion that isprepared by adding the filler material at higher solids content inpolymer latex, without subjecting the dispersion to substantialevaporation or other liquid removal. Remarkably, the barrier propertiesof the invention are superior to uncondensed formulations, even wherethe solids content and composition are the same. As compared to filmsformed from dispersions which did not undergo an evaporation step, theinventive coatings exhibit permeability values that are at least 10percent, and preferably at least 20 percent lower.

In addition to reduced gas permeability, the high solids coatingformulation produced in accordance with the present invention provides aproduct with reduced drying times, higher viscosity and thus thicker dipcoated samples in a single step, better suspension stability, reducedshipping costs, thicker spray coatings without dripping, reducedpenetration of coating into substrate porosity and defects, and thickercoating in continuous film and paper coating applications.

The substrate used with the inventive coatings is not particularlylimited and may include polymeric films, elastomeric substrates, metalfoils, and cellulosic substrates such as paper, paperboard, among othersubstrates. The substrates may be films, corrosion protective films,vacuum and controlled atmosphere packages, blow molded containers,thermoformed containers, and electronic display films among others.

According to one aspect of the invention, there is provided a method ofmaking an article of manufacture with a barrier coating film, including(a) preparing an aqueous dispersion which includes a matrix polymer andan exfoliated silicate filler material; (b) concentrated the dispersionby evaporating water therefrom, such that the solids content of thedispersion increases by 5 percent; (c) applying the concentrateddispersion to a substrate; and (d) drying the concentrated dispersion toproduce a barrier coating film which has a permeability that is at least200 times lower than a like coating film that is prepared without thesilicate filler material.

Suitable articles for the barrier coatings of the present inventioninclude gloves, tennis balls, basketballs, soccer balls, footballs,volley balls, racket balls, handballs, beach balls, and toy balls andinflated products such as automobile and truck tires, bicycle tires,boats, air mattresses and inflatable beds.

The coatings of the invention are particularly suitable for use inpackaging material, whereby the barrier coating is applied to apolymeric film substrate or paperboard substrate, and is used to packagegoods which are sensitive to gases such as oxygen, for example, food,drinks, electronic components, pharmaceuticals, and the like.

EXAMPLES

In the following examples, nanocomposite barrier coating films areprepared and applied to polyester film substrates, and then are testedfor oxygen transmission rate. The nanocomposite barrier coating filmsare prepared in an aqueous medium with a polyester resin (Eastek 1000,Eastman, 30% polymer solids) as the polymer matrix and montmorrillonite(SCPX-2973, SCPX-2953, or SCPX-2041) as the exfoliated silicate filler.

Experimental Procedures Oxygen Transmission Rate (OTR) Testing

Films and coated substrates are tested for oxygen transmission rateusing a Mocon OXTRAN 2/20 or 2/60 module at 23° C., 0% RH, and 1 atm.The samples are loaded onto the modules and conditioned for 2 hoursprior to testing for oxygen. Once equilibrium is reached, an OTR isreported in units of cc/m² day atm.

Thickness Measurements

All thickness calculations are based on the weight of the coating, andan assumed density. For the purposes of the present invention, thedensity for the polymer phase is assumed to be 0.95 gm/cc in all cases,even though it is recognized that each polymer has a different density.The density of the nanocomposite was estimated using a rule of mixtures,and an assumed density of the clay of 2 gm/cc.

The thickness of the coating on a substrate is measured after the OTR isreported. Each sample is removed from the Mocon module and a circle ofspecified size is cut from the sample. The cut circle is weighed. Theweight of the coating is obtained from subtracting the weight of theuncoated circle, and the thickness calculated from the size of thecircle and weight of the coating. For coating thickness less than 5microns, the thickness is measured using an optical profilometer. Thethickness of the film is reported in millimeters and used to calculatethe permeability of the film.

The permeability of the coatings is calculated as follows:

${{Permeability}\mspace{14mu} {of}\mspace{14mu} {barrier}\mspace{14mu} {coating}} = \frac{X_{1}}{\left\lbrack {\left( {{1/O}\; T\; R} \right) - \left( {X_{2}/P_{X\; 2}} \right)} \right\rbrack}$

where X₁ is the barrier coating thickness; X₂ is substrate thickness,P_(X2) is permeability of the substrate, and OTR is oxygen transmissionrate measured for the barrier coating. The reduction in permeability iscalculated as follows:

$\begin{matrix}{{Reduction}\mspace{14mu} {in}} \\{permeability}\end{matrix} = {\left\lbrack {1 - \frac{\begin{matrix}{{Permeability}\mspace{14mu} {of}\mspace{14mu} a\mspace{14mu} {barrier}\mspace{14mu} {coating}\mspace{20mu} {prepared}} \\{{according}\mspace{14mu} {to}\mspace{14mu} {the}\mspace{14mu} {inventive}\mspace{14mu} {method}}\end{matrix}}{\begin{matrix}{{Permeability}\mspace{14mu} {of}\mspace{14mu} a\mspace{14mu} {barrier}\mspace{14mu} {coating}} \\{{prepared}\mspace{14mu} {by}\mspace{14mu} {other}\mspace{14mu} {method}}\end{matrix}}} \right\rbrack \times 100\%}$

The benefit of obtaining the permeability of the coating versus the OTRof the sample is that permeability reports the OTR at a specifiedthickness. Therefore, coatings with different thicknesses can becompared directly. OTR units are cc/m² day at 1 atmosphere, 0% relativehumidity at 23° C.

Example 1A 5% Solids Polyester Nanocomposite Using SCPX-2973Montmorrillonite Slurry

In an 8 oz jar, 0.02 grams of Acusol® 880 (35.2%, Rohm & Haas), 0.05grams of Acusol® 882 (17.1%, Rohm & Haas) and 41.54 grams of distilledwater were weighed. A stir bar was added and the solution was stirreduntil the Acusol materials were dissolved. To this solution was added amixture of 5.65 grams of polyester latex (Eastek 1000, Eastman) and 1drop of Surfynol® PSA 336 (Air Products, 100%). The resulting solutionwas mixed thoroughly.

To the above solution, 14.25 grams of montmorrillonite SCPX-2973 slurry(9.21% silicate filler) was mixed with 3.49 grams of glycine (Lab SafetySupply, 20% glycine by weight) and 10 grams of distilled water. Theresulting solution was stirred with a stir bar for 1 hour and 1 drop ofMergal 680 (Troy Chemical Corporation, 26.3% by weight anti-microbial)was added. The percent solids of the formulation were measured as 5.0%,using standard techniques.

After this coating solution is applied to a polyester film substrate andallowed to dry, the coating contains 45.4% by weight polyester, 35.1% byweight filler, 18.7% glycine, 0.3% Surfynol® PSA 336 wetting agent, 0.2%by weight Acusol® 880, 0.2% by weight Acusol® 882 and 0.05% by weightMergal 680 anti-microbial agent.

The oxygen transmission rate (OTR) is measured using a MOCON® OX-TRAN2/20 module. The OTR is 11.9 cc/m² day @ 1 atmosphere, 0% RH, 23° C.Permeability of the 0.5 micron polyester nanocomposite is 0.008 cc mm/m²day atmosphere @ 0% RH, 23° C. The reduction in permeability of thiscoating is 337 times the reduction in permeability of a coating madefrom the unfilled polyester latex.

Example 1B 8% Solids Polyester Nanocomposite Using SCPX-2973Montmorrillonite Slurry

In an 8 oz jar, 0.04 grams of Acusol® 880 (35.2%, Rohm & Haas), 0.08grams of Acusol® 882 (17.1%, Rohm & Haas) and 37.4 grams of distilledwater were weighed. A stir bar was added and the solution was stirreduntil the Acusol® materials were dissolved. To this solution was added amixture of 9.0 grams of polyester latex (Eastek 1000, Eastman) and 1drop of Surfynol® PSA 336 (Air Products, 100%). The resulting solutionwas mixed thoroughly.

To the above solution, 22.8 grams of montmorrillonite SCPX-2973 slurry(9.21%) was mixed with 5.59 grams of glycine (Lab Safety Supply, 20%).The resulting solution was stirred with a stir bar for 1 hour and 1 dropof Mergal 680 (Troy Chemical Corporation, 26.3%) was added. The percentsolids of the formulation were measured as 8.1% using standardtechniques.

After this coating solution is applied to a polyester film substrate andallowed to dry, the coating contains 45.4% by weight polyester, 35.1% byweight filler, 18.7% glycine, 0.3% Surfynol® PSA 336 wetting agent, 0.2%by weight Acusol® 880, 0.2% by weight Acusol® 882 and 0.05% by weightMergal 680 anti-microbial agent.

The oxygen transmission rate (OTR) is measured using a MOCON® OX-TRAN2/20 module. The OTR is 6.1 cc/m² day @ 1 atmosphere, 0% RH, 23° C.Permeability of the 0.6 micron polyester nanocomposite is 0.004 cc mm/m²day atmosphere @ 0% RH, 23° C. The reduction in permeability of thiscoating is 675 times the reduction in permeability of a coating madefrom the unfilled polyester latex.

Example 1C 8% Solids Polyester Nanocomposite Using SCPX-2973Montmorrillonite Slurry Concentrated from Example 1A

50 grams of the nanocomposite from example 1A was placed in an 8 oz.jar. The jar with the lid removed was then placed into a water bath at95° C. for 90 min while stirring. The internal temperature of theformulation was maintained at 75° C. After the allotted time, theformulation was removed from the water bath and stirred overnight withthe lid replaced. The percent solids of the concentrated formulationwere measured as 8.3% using standard techniques.

After this coating solution is applied to a polyester film substrate andallowed to dry, the coating contains 45.4% by weight polyester, 35.1% byweight filler, 18.7% glycine, 0.3% Surfynol® PSA 336 wetting agent, 0.2%by weight Acusol® 880, 0.2% by weight Acusol® 882 and 0.05% by weightMergal 680 anti-microbial agent.

The oxygen transmission rate (OTR) is measured using a MOCON® OX-TRAN2/20 module. The OTR is 5.0 cc/m² day @ 1 atmosphere, 0% RH, 23° C.Permeability of the 0.6 micron polyester nanocomposite is 0.003 cc mm/m²day atmosphere @ 0% RH, 23° C. The reduction in permeability of thiscoating is 900 times the reduction in permeability of a coating madefrom the unfilled polyester latex. The permeability is also 25% lowerthan the dispersion that was prepared at a target solids content of 8%.

Example 2A 5% Solids Polyester Nanocomposite Using SCPX-2953Montmorrillonite Solid

In a 16 oz jar, 0.05 grams of Acusol® 880 (35.2%, Rohm & Haas), 0.1grams of Acusol® 882 (17.1%, Rohm & Haas) and 78.9 grams of distilledwater were weighed. A stir bar was added and the solution was stirreduntil the Acusol materials were dissolved. To this solution was added amixture of 11.3 grams of polyester latex (Eastek 1000, Eastman) and 2drop of Surfynol® PSA 336 (Air Products, 100%). The resulting solutionwas mixed thoroughly.

To the above solution, 2.63 grams of montmorrillonite SCPX-2953 solid(100%) was mixed with 6.98 grams of glycine (Lab Safety Supply, 20%) and50 grams of distilled water. The resulting solution was stirred with astir bar for 1 hour and 2 drops of Mergal 680 (Troy ChemicalCorporation, 26.3%) was added. The percent solids of the formulationwere measured as 4.8% using standard techniques.

After this coating solution is applied to a polyester film substrate andallowed to dry, the coating contains 45.4% by weight polyester, 35.1% byweight filler, 18.7% glycine, 0.3% Surfynol® PSA 336 wetting agent, 0.2%by weight Acusol® 880, 0.2% by weight Acusol® 882 and 0.05% by weightMergal 680 anti-microbial agent.

The oxygen transmission rate (OTR) is measured using a MOCON® OX-TRAN2/20 module. The OTR is 6.5 cc/m² day @ 1 atmosphere, 0% RH, 23° C.Permeability of the 0.5 micron polyester nanocomposite is 0.004 cc mm/m²day atmosphere @ 0% RH, 23° C. The reduction in permeability of thiscoating is 675 times the reduction in permeability of a coating madefrom the unfilled polyester latex.

Example 2B 8% Solids Polyester Nanocomposite Using SCPX-2953Montmorrillonite Solid

In an 8 oz jar, 0.04 grams of Acusol® 880 (35.2%, Rohm & Haas), 0.09grams of Acusol® 882 (17.1%, Rohm & Haas) and 38.16 grams of distilledwater were weighed. A stir bar was added and the solution was stirreduntil the Acusol materials were dissolved. To this solution was added amixture of 9.0 grams of polyester latex (Eastek 1000, Eastman) and 1drop of Surfynol® PSA 336 (Air Products, 100%). The resulting solutionwas mixed thoroughly.

To the above solution, 2.1 grams of montmorrillonite SCPX-2953 solid(100%) was mixed with 5.59 grams of glycine (Lab Safety Supply, 20%) and20 grams of distilled water. The resulting solution was stirred with astir bar for 1 hour and 1 drop of Mergal 680 (Troy Chemical Corporation,26.3%) was added. The percent solids of the formulation were measured as7.8% using standard techniques.

After this coating solution is applied to a polyester film substrate andallowed to dry, the coating contains 45.4% by weight polyester, 35.1% byweight filler, 18.7% glycine, 0.3% Surfynol® PSA 336 wetting agent, 0.2%by weight Acusol® 880, 0.2% by weight Acusol® 882 and 0.05% by weightMergal 680 anti-microbial agent.

The oxygen transmission rate (OTR) is measured using a MOCON® OX-TRAN2/20 module. The OTR is 11.5 cc/m² day @ 1 atmosphere, 0% RH, 23° C.Permeability of the 0.6 micron polyester nanocomposite is 0.009 cc mm/m²day atmosphere @ 0% RH, 23° C. The reduction in permeability of thiscoating is 300 times the reduction in permeability of a coating madefrom the unfilled polyester latex.

Example 2C 8% Solids Polyester Nanocomposite Using SCPX-2953Montmorrillonite Solid Concentrated from Example 2A

50 grams of the nanocomposite formulation of example 2A was placed in an8 oz. jar. The jar with the lid removed was then placed into a waterbath at 95° C. for 90 min while stirring. The internal temperature ofthe formulation was maintained at 75° C. After the allotted time, theformulation was removed from the water bath and stirred overnight withthe lid replaced. The percent solids of the formulation was measured as7.8% using standard techniques.

After this coating solution is applied to a polyester film substrate andallowed to dry, the coating contains 45.4% by weight polyester, 35.1% byweight filler, 18.7% glycine, 0.3% Surfynol® PSA 336 wetting agent, 0.2%by weight Acusol® 880, 0.2% by weight Acusol® 882 and 0.05% by weightMergal 680 anti-microbial agent.

The oxygen transmission rate (OTR) is measured using a MOCON® OX-TRAN2/20 module. The OTR is 3.0 cc/m² day @ 1 atmosphere, 0% RH, 23° C.Permeability of the 0.6 micron polyester nanocomposite is 0.002 cc mm/m²day atmosphere @ 0% RH, 23° C. The reduction in permeability of thiscoating is 1350 times the reduction in permeability of a coating madefrom the unfilled polyester latex. The permeability is also 78% lowerthan the dispersion that was prepared at a target solids content of 8%.

Example 3A 5% Solids Polyester Nanocomposite Using SCPX-2041Montmorrillonite Solid

In a 16 oz jar, 0.05 grams of Acusol® 880 (35.2%, Rohm & Haas), 0.1grams of Acusol® 882 (17.1%, Rohm & Haas) and 78.94 grams of distilledwater were weighed. A stir bar was added and the solution was stirreduntil the Acusol materials were dissolved. To this solution was added amixture of 11.3 grams of polyester latex (Eastek 1000, Eastman) and 2drop of Surfynol® PSA 336 (Air Products, 100%). The resulting solutionwas mixed thoroughly.

To the above solution, 2.63 grams of montmorrillonite SCPX-2041 solid(100%) was mixed with 6.98 grams of glycine (Lab Safety Supply, 20%) and50 grams of distilled water. The resulting solution was stirred with astir bar for 1 hour and 2 drops of Mergal 680 (Troy ChemicalCorporation, 26.3%) was added. The percent solids of the formulationwere measured as 5.0% using standard techniques.

After this coating solution is applied to a polyester film substrate andallowed to dry, the coating contains 45.4% by weight polyester, 35.1% byweight filler, 18.7% glycine, 0.3% Surfynol® PSA 336 wetting agent, 0.2%by weight Acusol® 880, 0.2% by weight Acusol® 882 and 0.05% by weightMergal 680 anti-microbial agent.

The oxygen transmission rate (OTR) is measured using a MOCON® OX-TRAN2/20 module. The OTR is 17.1 cc/m² day @ 1 atmosphere, 0% RH, 23° C.Permeability of the 0.5 micron polyester nanocomposite is 0.013 cc mm/m²day atmosphere @ 0% RH, 23° C. The reduction in permeability of thiscoating is 207 times the reduction in permeability of a coating madefrom the unfilled polyester latex.

Example 3B 8% Solids Polyester Nanocomposite Using SCPX-2041Montmorrillonite Solid

In an 8 oz jar, 0.04 grams of Acusol® 880 (35.2%, Rohm & Haas), 0.09grams of Acusol® 882 (17.1%, Rohm & Haas) and 38.16 grams of distilledwater were weighed. A stir bar was added and the solution was stirreduntil the Acusol materials were dissolved. To this solution was added amixture of 9.02 grams of polyester latex (Eastek 1000, Eastman) and 1drop of Surfynol® PSA 336 (Air Products, 100%). The resulting solutionwas mixed thoroughly.

To the above solution, 2.1 grams of montmorrillonite SCPX-2041 solid(100%) was mixed with 5.59 grams of glycine (Lab Safety Supply, 20%) and20 grams of distilled water. The resulting solution was stirred with astir bar for 1 hour and 1 drop of Mergal 680 (Troy Chemical Corporation,26.3%) was added. The percent solids of the formulation were measured as7.8% using standard techniques.

After this coating solution is applied to a polyester film substrate andallowed to dry, the coating contains 45.4% by weight polyester, 35.1% byweight filler, 18.7% glycine, 0.3% Surfynol® PSA 336 wetting agent, 0.2%by weight Acusol® 880, 0.2% by weight Acusol® 882 and 0.05% by weightMergal 680 anti-microbial agent.

The oxygen transmission rate (OTR) is measured using a MOCON® OX-TRAN2/20 module. The OTR is 9.7 cc/m² day @ 1 atmosphere, 0% RH, 23° C.Permeability of the 0.6 micron polyester nanocomposite is 0.007 cc mm/m²day atmosphere @ 0% RH, 23° C. The reduction in permeability of thiscoating is 386 times the reduction in permeability of a coating madefrom the unfilled polyester latex.

Example 3C 8% Solids Polyester Nanocomposite Using SCPX-2041Montmorrillonite Solid Concentrated from Example 3A

50 grams of the nanocomposite formulation from Example 3A was placed inan 8 oz. jar. The jar with the lid removed was then placed into a waterbath at 95° C. for 90 min while stirring. The internal temperature ofthe formulation was maintained at 75° C. After the allotted time, theformulation was removed from the water bath and stirred overnight withthe lid replaced. The percent solids of the formulation were measured as9.0% using standard techniques.

After this coating solution is applied to a polyester film substrate andallowed to dry, the coating contains 45.4% by weight polyester, 35.1% byweight filler, 18.7% glycine, 0.3% Surfynol® PSA 336 wetting agent, 0.2%by weight Acusol® 880, 0.2% by weight Acusol® 882 and 0.05% by weightMergal 680 anti-microbial agent.

The oxygen transmission rate (OTR) is measured using a MOCON® OX-TRAN2/20 module. The OTR is 7.5 cc/m² day @ 1 atmosphere, 0% RH, 23° C.Permeability of the 0.6 micron polyester nanocomposite is 0.005 cc mm/m²day atmosphere @ 0% RH, 23° C. The reduction in permeability of thiscoating is 540 times the reduction in permeability of a coating madefrom the unfilled polyester latex. The permeability is also 28% lowerthan the dispersion that was prepared at a target solids content of 8%.

The permeability data for Examples 1A through 3C are outlined in Table1, below.

TABLE 1 Summary of Results Oxygen Permeability (cc mm/m2 day atm @ 23C., 0% RH) Example 5% solid 8% as made 8% concentrated Ex. 1A-1C 0.0080.004 0.003 SCPX-2973 slurry Ex. 2A-2C 0.0035 0.009 0.0025 SCPX-2953solid Ex. 3A-3C 0.013 0.007 0.005 SCPX-2041 solid

The above results are further illustrated in FIG. 1, where it can beseen that for each composition, the 8% concentrated dispersions of theinvention achieved the best barrier properties. This is surprisingbecause, aside from the method of preparation, one would think that thecomposition and structure would be substantially identical to thosewhich were prepared at an 8% solids level. Moreover, the improvement isdramatic, with the concentrated dispersions providing coatings whichhave permeability values which are 20% lower than the 8% as-madecomposition, and in some instances show improvements of more than 70%.

While the invention has been described in connection with severalembodiments, modifications of those embodiments within the spirit andscope of the present invention will be readily apparent to those ofskill in the art. The invention is defined in the appended claims.

1. A concentrated nanocomposite dispersion for forming a barrier coatingon a substrate, said dispersion comprising: a) a liquid carrier mediumwhich includes primarily water; b) an exfoliated silicate fillermaterial dispersed in the carrier medium; and c) a matrix polymer whichis dispersed in the carrier medium, wherein the concentrated dispersionis prepared by dispersing the filler material and the polymer matrix inthe liquid carrier medium, and increasing the solids content of theinitial dispersion by at least 5% by selectively removing a portion ofthe liquid carrier medium prior to application on the substrate.
 2. Theconcentrated nanocomposite dispersion according to claim 1, wherein thesolids content of the initial dispersion is increased by at least 25% byselectively removing a portion of the liquid carrier medium.
 3. Theconcentrated nanocomposite dispersion according to claim 1, wherein thesolids content of the initial dispersion is increased by at least 50% byselectively removing a portion of the liquid carrier medium.
 4. Theconcentrated nanocomposite dispersion according to claim 1, wherein thesolids content of the initial dispersion is increased by evaporating offa portion of the liquid carrier medium.
 5. The concentratednanocomposite dispersion according to claim 1, wherein the concentrateddispersion has a solids content in the range of from 5 to 25 weightpercent.
 6. The concentrated nanocomposite dispersion according to claim1, wherein the concentrated dispersion has a solids content in the rangeof from 7 to 15 weight percent.
 7. The concentrated nanocompositedispersion according to claim 1, wherein the exfoliated silicate filtermaterial includes a compound selected from the group consisting ofbentonite, vermiculite, montmorillonite, nontronite, beidellite,volkonskoite, hectorite, saponite, laponite, sauconite, magadiite,kenyaite, ledikite, and combinations thereof.
 8. The concentratednanocomposite dispersion according to claim 1, wherein the exfoliatedsilicate filler material includes montmorillonite.
 9. The concentratednanocomposite dispersion according to claim 1, wherein the exfoliatedsilicate filler material comprises platelets with an average aspectratio of at least
 50. 10. The concentrated nanocomposite dispersionaccording to claim 1, wherein the exfoliated silicate filler materialcomprises platelets with an average aspect ratio of at least 1,000. 11.The concentrated nanocomposite dispersion according to claim 1, whereinthe exfoliated silicate filler material comprises platelets with anaverage aspect ratio of at least 5,000.
 12. The concentratednanocomposite dispersion according to claim 1, wherein the matrixpolymer includes a polymer selected from the group consisting ofpolyesters, polyamides, chlorinated polymers, polyolefins,polyurethanes, polyethers, polyketones, polycarbonates, acrylics,vinylics, flouropolymers, and combinations thereof.
 13. The concentratednanocomposite dispersion according to claim 1, wherein the matrixpolymer includes a polyester resin.
 14. The concentrated nanocompositedispersion according to claim 1, wherein the matrix polymer includes asulfonated polyester resin.
 15. The concentrated nanocompositedispersion according to claim 1, wherein the concentrated dispersionfurther includes at least one adjuvant selected from the groupconsisting of surfactants, anti-foaming agents, dispersing agents,wetting agents, leveling agents and thickeners.
 16. A nanocompositebarrier coating which is prepared by forming a film from theconcentrated dispersion in claim
 1. 17. The nanocomposite barriercoating according to claim 16, wherein the coating exhibits an oxygenpermeability that is at least 10 percent lower than a like coating thatis prepared with a like dispersion which is not concentrated byselectively removing a portion of the liquid carrier medium.
 18. Thenanocomposite barrier coating according to claim 16, wherein the coatingexhibits an oxygen permeability that is at least 20 percent lower than alike coating that is prepared with a like dispersion which is notconcentrated by selectively removing a portion of the liquid carriermedium.
 19. The nanocomposite barrier coating according to claim 16,wherein the coating exhibits an oxygen permeability of less than 0.02cc-mm/m²-day-atm.
 20. The nanocomposite barrier coating according toclaim 16, wherein the coating exhibits an oxygen permeability of lessthan 0.01 cc-mm/m²-day-atm.
 21. A packaging film which comprises thebarrier coating according to claim 16 adhered to a polymeric substrate.22. A packaging material which comprises the barrier coating accordingto claim 16 adhered to a cellulosic substrate.
 23. An article with anoxygen barrier coating layer, said article comprising: a) a substrate;and b) a barrier coating layer adhered to the substrate, where thebarrier coating layer includes an exfoliated silicate filler materialand a matrix polymer, wherein said barrier coating layer is preparedfrom an aqueous dispersion which is concentrated by at least 5 percentby evaporating water from the dispersion prior to application on thesubstrate.
 24. The article according to claim 23, wherein the substrateis a cellulosic substrate.
 25. The article according to claim 24,wherein the cellulosic substrate is paperboard.
 26. Packaging film withan oxygen barrier coating layer, said packaging film comprising: a) apolymeric film substrate; and b) a barrier coating layer adhered to thepolymeric film, where the barrier coating layer includes an exfoliatedsilicate filler material and a matrix polymer, wherein said barriercoating layer is prepared from an aqueous dispersion which isconcentrated by at least 5 percent by evaporating water therefrom priorto application on the polymeric film.
 27. A method for producing anarticle of manufacture with a barrier coating film, said methodcomprising the steps of: a) preparing an aqueous dispersion whichincludes a matrix polymer and an exfoliated silicate filler material; b)concentrating the dispersion by evaporating water therefrom such thatthe solids content of the dispersion is increased by at least 5%; c)applying a layer of the concentrated dispersion to a substrate; and d)drying the concentrated dispersion to produce a barrier coating filmwhich exhibits a permeability that is at least 200 times lower than alike coating film which does not include silicate filler material. 28.The method according to claim 27, wherein said substrate is selectedfrom the group consisting of antiseptic packaging films, corrosionprotective films, vacuum and controlled atmosphere packages, blow moldedcontainers, thermoformed containers and electronic display films.